1. Field of the Invention
This invention relates generally to the making, or lasting, of shoes, and particularly to method and apparatus for the fluid lasting of shoes and the performance of similar operations.
2. Description of the Prior Art
Lasting is the making of a shoe. All preliminary operations--for example, cutting, stitching or sewing, and the like--are staffed by less skilled operators and scheduled according to the productive capacity of the lasting operation. Further, all subsequent operations--for example, sole and heel spotting, inspection, packing and shipping, and the like--are dependent upon the lasters. Here, as well, the quality of the labor is less skilled and less expensive.
Many of the lower quality or special shoes, such as rubbers, tennis shoes, and the like, are lasted, or formed, by extrusion. But, this method is not suitable to the fabrication of medium and high quality shoes. Consequently, most of the latter mentioned shoes are still lasted primarily by hand. Machines have been developed that will last the toe and/or heel of the shoe, but not the entire shoe. These machines have been helpful in providing uniform quality to partial lasting and provide physical power for partially lasting some materials that cannot be readily managed by hand. In addition, there is a machine, generally referred to as the "Kamborian", that can completely last a shoe in one operation, but the high degree of skill required by the operator renders qualified labor in short supply and prohibitively expensive. In addition, this known machine cannot handle materials that are either too soft or too stiff.
Early in this century, it was recognized that a need existed for better--that is, faster and less expensive--ways to last a shoe. Any solution, naturally, would minimize the physical effort and operator skill required. While the solutions that were formulated tended to minimize the physical effort required, the resulting splitting of the operation into several parts to reduce the skill necessary to do the job only succeeded in increasing costs and, in many cases, created a safety hazard for the operator.
While it was recognized early that it would be desirable to accomplish the lasting operation by use of fluid pressure which would wipe an upper to an insole, attempts to construct devices to last shoes in such a manner proved impractical because of inability to properly control the wiping action of an elastic sheet and the like, acting under fluid pressure. By "to wipe" is meant the operation wherein the peripheral portions of an upper are folded over and secured to an insole, with the upper being, of course, the material that encloses the foot within a shoe. Thus, early attempts to achieve a fluid lasting of shoes, such as shown in, for example, U.S. Pat. Nos. 761,356, issued May 31, 1904 to W. H. Burritt, and 1,261,959, issued Apr. 9, 1918 to R. Reid, leave the wiping of the upper to the insole as a subsequent manual operation.
U.S. Pat. No. 3,422,475, issued Jan. 21, 1969 to H. H. Hart, discloses a lasting arrangement wherein the last is rammed into an elastomeric sheet which supports the upper. In particular, this patent states in column 4, lines 69 through 75, and column 5, lines 1 and 2, that the expansion of an elastomeric sheet about the last, while possible, is undesirable because of inability to control the wiping action of the elastomeric sheet on the last. Thus, the latter mentioned approach is generally not in use, although the advantages of such a technique are widely known in the art.